It peaked at 4.05% in March. The last 2 months it went just below 4% as the Unknown category increased. For June the reverse happened, so 4.04% seems to be the real current share of Linux on Desktop as desktop clients were read properly/werent spoofed.
Neither Cinnamon, XFCE or Mate have stable Wayland support. You need GNOME or Plasma for that if you want a desktop (or wait for the new Cosmic desktop and new PopOS)